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unknown user
09-05-2000, 07:28 PM
Dear Biomch-L Subscribers:

An important issue when investigating the properties of force plates is the
resonance frequency which limits the range of frequencies that can be
recorded without distortion. Now, I have a couple of questions regarding
Kistler plates fixed on the 4 sensors in the corners:

1) What exactly is meant by the resonance frequency of a given plate:
a) the frequencies of the vibrations within the plate considered as a rigid
body between its points of support or
b) the frequencies of the system as a whole meaning the plate together with
the base of support.
Maybe a comparison with a car on 4 wheels makes the difference a little
clearer: case a) corresponds to vibrations with in the chassis and case b)
to vibrations of the whole car on its wheels.

2) For experimental determination of the resonance frequency I looked at the
methods of modal analysis: they all do require the mesaurement of either
acceleration, velocity or movement which is not an easy thing to do with the
plates already installed.
However, it seems to me that it should be possible to get some idea of the
resonance properties of the plate by 'hammering' on one of the sensors and
measuring the force responses on all of the 4 sensors.
a) Is there any opinion on what information one can get from this kind of
measurement?
b) Is it possible to separate the two different kinds of vibrations ( point
1) ) in the signals and how?

3) Regarding the (experimental) analysis of force plates I only could find
two papers:
Bobbert, MF and Schamhardt, HC, 1990, Accuracy of Determining the Point of
Force Application with Piezoelectric Force Plates, jbiomech, 23(7):705-710.
Schmiedmayer, HB and Kastner, J, 1999, Parameters Influencing the Accuracy
of Point of Force Application Determined with Piezoelectric Force Plates,
jbiomech, 32:1237-1242.
Does anyone know about other work on this subject?

I appreciate any contribution and will post a summary of the responses,

regards,
Matthias

************************************************** *******************
*** Matthias Schablowski
*** Abt. Forschung 2: Laufbandlokomotion
*** Schlierbacher Landstrasse 200a
*** 69118 Heidelberg
***
*** Tel: ++49-6221-969284
*** Fax: ++49-6221-969234
*** Email: Matthias.Schablowski@ok.uni-heidelberg.de
************************************************** *******************

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